Refrigerator defroster



139., c. M. CHAPMAN REFRIGERATOR DEFROSTER Filed Sept. 13, 1937INVENTOR.

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Patented Oct. 31, 1939 2.11am aarnmam'roa nsmos'rmi Clifford M. Chapman,lmiianapolll M, assign or of two-thirdsto Bil-ell B.

one-third to And: Storm. both of Indianapolis, Ind.

Application September 18, 198?, Serial No. 183,544

30laiml.

This invention relates to a defrosting device for refrigerator unitswhich is particularly adaptable to mechanical refrigerators of thehousehold type. In order that such refrigerators may I be operated atthe maximum efliciency, it is necessary to remove the frost on therefrigerating unit at periodic intervals. This is generally accomplishedby stopping the refrigerating action and permitting the temperaturewithin the re- 10 frigerator to rise above the freezing point for asufficient length of time to melt the frost from the unit. The timeconsumed in defrosting the refrigerator by this method is relativelygreat since the temperature of the whole interior must 15 be raised.This increase in temperature is also objectionable since it defeats thevery purpose of the refrigerator.

Attempts have been made to defrost a refrigerator by electrical means bythe use of a resisgo tance heating unit placed in position to supplyheat to the refrigerating unit. Such methods reduce the time requiredfor defrosting and prevent an undue increase in temperature of therefrigerator. One object of the present invention is to provide anelectrical means for defrosting the cooling unit of a. refrigerator inthe shortest time with the smallest rise in temperature of therefrigerator as a whole. This is accomplished by placing the heatingelement in such position that transmitted by direct conduction to theheat transfer surfaces of the cooling unit on which the frost collects.

Another object of the invention is to provide 35 means for mounting thedefrosting elements in such manner that they may be quickly assembled asan accessory in a refrigerator already in use and may be attached tovarious types and sizes of refrigerating units without mechanicalchange. Other objects and features of the invention will be understoodfrom the accompanying drawing and the following description and claims,

Fig. 1 is a sectional view through the upper portion of a householdrefrigerator showing the 48 cooling unit in side elevation with adefrosting unit attached thereto. Fig. 2 is a perspective view of aportion of the defrosting unit.

In the form of the invention shown by way of illustration in thedrawing, there is illustrated 50 the upper portion of a refrigerator lhaving the usual door II and cooling unit l2 suitably mounted therein.The cooling unit herein shown is provided with a manifold l3 havingconnected thereto a plurality of refrigerant conductors I4 55 which passdown the side of the unit across the all, or nearly all of the heatgenerated therein isbottom and upwardly to a similar manifold on theopposite side not shown. The refrigerant conductors Il may be suppliedwith refrigerant at a low temperature inany well known manner and serveas the principal heat transfer surface 5 of the cooling unit. Theyare-normally in direct conductive relation with the walls of the unit I2proper.

Beneath the unit I2 there is provided an electrical resistance heatingelement of a common form enclosed in a U-shaped metallic tube It. Saidtube is held in position beneath the unit by a supporting cross piece Ithaving adjustable hooks ll secured to its ends. A tension spring I. issecured to the hooks l1 and passes over the unit l2. A metallic plate I9is preferably interposed between the U-shaped tube l5 and the lowerportion of the refrigerant, conductors it. The resistance element withinthe tube i5 is supplied with electricity by conductors passing throughan insulated cable 20 to a switch 2| which is in turn connected by acable 22 to any suitable source of electric current. The switch 2i isprovided with' ajbutton 22 by means of which the current tothe heatingelement may be manually turned on. The switch is provided with athermostat bellows 23 connected by a tube 24 to a thermostat bulb 25.The bulb 25 is placed in contact with the walls of the cooling unit andthe bellows 23 operates the switch in a well known manner to turn offthe heating current when the temperature at the bulb 25 risessufficiently above the melting point to melt the frost on the unit.

By means of. this construction, the defrosting of the refrigerator maybe accomplished in a rapid and efllcient manner with a minimum ofattention from the housewife. It is only necessary for the housewife tooperate the switch 2i without disturbing the action of the refrigeratingunit. The heat from the resistance element within the tube 15 is largelytransmitted by direct conduction to the plate i9 and distributed by saidplate by direct conduction to the refrigerant conductors l5 and thenceto the walls of the unit. The heat radiated from the tube I5 and theplate I!) to the interior of the ice box as a whole is a very smallpercentage of the heat generated, since these surfaces prior todefrosting are generally at a low temperature and are themselves coveredwith 60 frost due to their direct conductive relation with therefrigerant conductors It. The temperature of the heat transfer surfacescan be raised very rapidly and as soon as this temperature has increasedto a point at which the frost will be melted,

the heat is automatically turned oil without attention from thehousewife.

The resilient mounting of the heating unit beneath the cooling unitprovides that it may be quickly attached to almost any size ofthe'cooling unit and, therefore, does not need to be designed to fit aparticular refrigerator. It may be installed by unskilled labor and mayeasily be installed in refrigerators already in service. The switch 2|,of course, may be supported by any suitable means anywhere within therefrigerator.

While the foregoing specification describes in detail a preferred formof the invention, the various elements thereof may be variedby thoseskilled in the art without departing from the scope of the invention asdefined in the appended claims.

The invention claimed is:

1. In combination with the cooling unit of a refrigerator, a plate ofheat conducting material engaging at least a portion of the heattransfer surface of said cooling unit, an electrical resistance heatingunit engaging the opposite face of said plate, an elongated tensionspring passing about said cooling unit, and means attached to the endsof said spring for supporting said heating unit in contact with saidplate, and said plate in contact with said cooling unit.

2. In a refrigerator having a cooling unit with refrigerant conductorsarranged about the outside thereof, the combination of a plate of heatconducting material engaging at least a part of the outer surfaces ofsaid refrigerant conductors,

-an electrical resistance heating unit engaging the opposite face ofsaid plate, an elongated tension spring passing about said cooling unit,and means attached to the ends of said spring for supporting saidheating unit in contact with said plate, and said plate in contact withsaid cooling unit.

3. In combination with the cooling unit of a refrigerator, an electricalresistance heating element, heat transfer means interposed between saidelement and at least a portion of the heat transfer surface of saidcooling unit, an elongated tension spring passing about said coolingunit, and means attached to the ends of said spring for supporting saidheating element and said heat transfer means in heat transfer relationto said cooling unit.

CLIFFORD M. CHAPMAN.

